Monoalkyl tin compounds with low polyalkyl contamination, their compositions and methods

ABSTRACT

A pure composition comprises a monoalkyltin trialkoxide compound represented by the chemical formula RSn(OR′) 3  or a monoalkyl tin triamide compound represented by the chemical formula RSn(NR′ 2 ) 3  and no more than 4 mole % dialkyltin compounds relative to the total tin amount, where R is a hydrocarbyl group with 1-31 carbon atoms, and wherein R′ is a hydrocarbyl group with 1-10 carbon atoms. Methods are described for the formation of the pure compositions. A solid composition comprises a monoalkyl triamido tin compound represented by the chemical formula RSn—(NR′COR″) 3 , where R is a hydrocarbyl group with 1-31 carbon atoms, and where R′ and R″ are independently a hydrocarbyl group with 1-10 carbon atoms. The compositions are suitable for the formation of resist compositions suitable for EUV patterning in which the compositions have a high EUV absorption.

CROSS REFERENCE TO RELATED APPLICATIONS

This divisional application claims priority to copending U.S. patentapplication Ser. No. 15/950,292 filed Apr. 11, 2018 to Edson et al.,entitled “Monoalkyl Tin Compounds with Low Polyalkyl Contamination,Their Compositions And Methods,” which is incorporated herein byreference.

FIELD OF THE INVENTION

The invention relates to high-purity compositions of monoalkyl tintriamides, monoalkyl tin trialkoxides, or monoalkyl triamido tin and themethods to make them.

BACKGROUND OF THE INVENTION

Organometallic compounds are of interest for providing metal ions in asolution processable form. Alkyl tin compounds provide a radiationsensitive Sn—C bond that can be used to pattern structureslithographically. The processing of semiconductor materials with evershrinking dimensions results in demands for more versatile materials toachieve desired patterning resolution, and alkyl tin compounds arepromising advanced materials to provide patterning advantages.

SUMMARY OF THE INVENTION

In a first aspect, the invention pertains to a composition comprising amonoalkyltin trialkoxide compound represented by the chemical formulaRSn(OR′)₃ or a monoalkyl tin triamide compound represented by thechemical formula RSn(NR′₂)₃ and no more than 4 mole % dialkyltincompounds relative to the total tin amount, where R is a hydrocarbylgroup with 1-31 carbon atoms, and where R′ is a hydrocarbyl group with1-10 carbon atoms. The monoalkyl tin triamide can be reacted with analcohol represented by the formula HOR″ in an organic solvent to formRSn(OR″)₃, wherein R″ is independently a hydrocarbyl group with 1-10carbon atoms to form a product composition, wherein the productcomposition has no more than 4 mole % dialkyltin compounds relative tothe total amount of tin.

In a further aspect, the invention pertains to a composition comprisinga monoalkyl triamido tin compound represented by the chemical formulaRSn—(NR′COR″)₃, where R is a hydrocarbyl group with 1-31 carbon atoms,and where R′ and R″ are independently a hydrocarbyl group with 1-10carbon atoms.

In another aspect, the invention pertains to a method to form amonoalkyltin triamide compound, the method comprising, reacting analkylating agent selected from the group consisting of RMgX, R₂Zn,RZnNR′₂, or a combination thereof, with Sn(NR′₂)₄ in a solutioncomprising an organic solvent, where R is a hydrocarbyl group with 1-31carbon atoms, where X is a halogen, and where R′ is a hydrocarbyl groupwith 1-10 carbon atoms.

In other aspects, the invention pertains to a method to selectively forma monoalkyltin trialkoxide compound with low dialkyl tin contamination,the method comprising reacting RSn(NR′₂)₃ with an alcohol represented bythe formula HOR″ in an organic solvent to form RSn(OR″)₃, wherein theRSn(NR′₂)₃ reactant has no more than about 4 mole % dialkyl tincontaminants and is the product of the method of claim 17, where R is ahydrocarbyl group with 1-31 carbon atoms, and where R′ and R″ areindependently a hydrocarbyl group with 1-10 carbon atoms.

In additional aspects, the invention pertains to a method for formingmonoalkyl triamido tin, the method comprising reacting a monoalkyltintriamide compound represented by the chemical formula RSn(NR′₂)₃ with anamide (R″CONHR″′) in an organic solvent, wherein R is a hydrocarbylgroup with 1-31 carbon atoms, and wherein R′, R″ and R″′ areindependently a hydrocarbyl with 1-8 carbon atoms; and collecting asolid product represented by the formula RSn(NR″′COR″)₃.

Moreover, the invention pertains to a method for forming a monoalkyl tintrialkoxide, the method comprising reacting a monoalkyl triamido tincompound (RSn(NR″′COR″)₃) with an alkali alkoxide compound (QOR′, whereQ is an alkali metal atom) in an organic solvent to form a productcompound represented by the chemical formula RSn(OR′)₃, wherein R is ahydrocarbyl group with 1-31 carbon atoms and wherein R′, R″ and R″′ areindependently a hydrocarbyl group with 1-10 carbons.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a ¹H NMR spectrum of t-BuSn(NMe₂)₃ synthesized with a Grignardreagent.

FIG. 2 is a ¹¹⁹Sn NMR spectrum of t-BuSn(NMe₂)₃ correspondingly used toobtain the spectrum in FIG. 1.

FIG. 3 is a ¹H NMR spectrum of CySn(NMe₂)₃ (Cy=cyclohexyl) synthesizedwith an alkyl zinc halide reagent.

FIG. 4 is a ¹¹⁹Sn NMR spectrum of CySn(NMe₂)₃ correspondingly used toobtain the spectrum in FIG. 3.

FIG. 5 is a ¹H NMR spectrum of CyHpSn(NMe₂)₃ synthesized with an dialkylzinc reagent.

FIG. 6 is a ¹¹⁹Sn NMR spectrum of CyHpSn(NMe₂)₃ correspondingly used toobtain the spectrum in FIG. 5.

FIG. 7 is a ¹H NMR spectrum of t-BuSn(NMe₂)₃ synthesized with a Grignardreagent and a neutral base.

FIG. 8 is a ¹¹⁹Sn NMR spectrum of t-BuSn(NMe₂)₃ correspondingly used toobtain the spectrum in FIG. 7.

FIG. 9 is a ¹H NMR spectrum of t-BuSn(Ot-Am)₃ synthesized fromt-BuSn(NMe₂)₃.

FIG. 10 is a ¹¹⁹Sn NMR spectrum of t-BuSn(Ot-Am)₃ correspondingly usedto obtain the spectrum in FIG. 9.

FIG. 11 is structure of t-butyltris(N-methylacetamido)tin(IV) obtainedby X-ray structure determination of a crystalline product.

FIG. 12 is a ¹H NMR spectrum of t-butyltris(N-methylacetamido)tin(IV).

FIG. 13 is a ¹¹⁹Sn NMR spectrum oft-butyltris(N-methylacetamido)tin(IV).

FIG. 14 is a ¹H NMR spectrum of t-BuSn(Ot-Am)₃ synthesized fromt-butyltris(N-methylacetamido)tin(IV).

FIG. 15 is a ¹¹⁹Sn NMR spectrum of t-BuSn(Ot-Am)₃ synthesized fromt-butyltris(N-methylacetamido)tin(IV).

FIG. 16 is a ¹¹⁹Sn NMR spectrum of t-BuSn(NMe₂)₃ spiked witht-Bu₂Sn(NMe₂)₂. The signal at 85.48 ppm corresponds to t-BuSn(NMe₂)₃,the signal at 56.07 ppm corresponds to (t-Bu)₂Sn(NMe₂)₂.

FIG. 17 is a ¹¹⁹Sn NMR spectrum of t-BuSn(NMe₂)₃ from the first fractioncollected by fractional distillation of the sample of FIG. 16.

FIG. 18 is a ¹¹⁹Sn NMR spectrum of t-BuSn(NMe₂)₃ from the secondfraction collected by fractional distillation of the sample of FIG. 16.

FIG. 19 is a ¹¹⁹Sn NMR spectrum of t-BuSn(NMe₂)₃ from the third fractioncollected by fractional distillation of the sample of FIG. 16.

DETAILED DESCRIPTION OF THE INVENTION

Methods have been found to obtain monoalkyl tin compositions, inparticular monoalkyl tin triamides, monoalkyl tin trialkoxides, andmonoalkyltrimido tin, with low polyalkyl tin byproducts. In particular,three approaches have been developed for the synthesis of monoalkyl tintriamides with relatively low polyalkyl tin byproducts that can be usedas synthesized or further purified. The selectively synthesizedmonoalkyl tin triamides can then be used to synthesize monoalkyl tintrialkoxides with correspondingly low polyalkyl tin byproducts.Furthermore, monoalkyl tin triamides, whether or not pure, can bereacted in solution to form solid monoalkyl triamido tin that excludesthe polyalkyl byproducts in the crystal such that the process is foundto be effective to form the monoalkyl triamido tin with low polyalkylbyproducts. The synthesized monoalkyl tin amides and monoalkyl tinalkoxides can be further purified by fractional distillation toeffectively reduce polyalkyl contaminants below levels that may alreadybe relatively low from the direct synthesis. Analytical techniques canbe used to evaluate the contaminant levels. In some embodiments,quantitative NMR (qNMR) shows byproducts can be reduced toconcentrations below 1 mole percent. The product tin compositions can beuseful as precursors for the synthesis of desirable patterningmaterials. For the application as precursors for patterning materials,the reduction of polyalkyl tin byproducts can be useful with respect tothe properties of the monoalkyl tin product compositions for use as EUVand UV photoresists or electron-beam patterning resists.

Monoalkyl tin triamides can be useful intermediate products in thepreparation of organotin photoresists. Methods for the preparation ofmonoalkyl tin triamides have previously employed lithium reagents toconvert tin tetraamides to the desired triamides. For example, t-butyltris(diethylamido)tin, (t-BuSn(NEt₂)₃), can be synthesized with alithium reagent according to the method of Hänssgen, D.; Puff, H.;Beckerman, N. J. Organomet. Chem. 1985, 293, 191, incorporated herein byreference. These methods with lithium reagents, however, can produce amixture of monoalkyl and dialkyl tin products. Also, lithiumcontaminants can be undesirable for semiconductor applications. Reportedmethods to prepare monoalkyl tin triamides containing a secondary alkylgroup produce mixtures rich in mono-, di-, and triakyl tin products. Asexplained below, it can be desirable to reduce any polyalkyl byproducts,e.g., dialkyl tin contaminants. While the monoalkyl and dialkyl speciescan be separated from each other for some compounds, the separation orpurification process generally raises the cost of manufacturing, andentrained dialkyl impurities may compromise the performance ofdownstream photoresist products. Thus, it can be desirable to synthesizethe monoalkyl tin compounds with higher purity such that any subsequentpurification, such as with fractional distillation, if desired, resultsin even lower dialkyl or polyalkyl contamination. If the as-synthesizedcompositions are sufficiently pure, a further purification by fractionaldistillation can be avoided.

The use of high purity monoalkyl tin compounds, especially mercaptocompounds as polymer stabilizers, is described in U.S. Pat. No.8,198,352 to Deelman et al., entitled “High Purity MonoalkyltinCompounds and Uses Thereof,” and U.S. Pat. No. 9,745,450 to Frenkel etal., entitled “Stabilizers Containing High Purity Mono-AlkyltinCompounds,” both of which are incorporated herein by reference. Thesepatents describe the formation of pure monoalkyl halides as precursorsfor the synthesis of the stabilizer compounds. The processes describedherein are focused on the synthesis of highly pure monoalkyl tintriamide, monoalkyl tin trialkoxide, or monoalkyl triamido tin compoundsusing distinct and effective synthesis approaches, which can be used inconjunction with fractional distillation for purification.

The use of alkyl metal coordination compounds in high performanceradiation-based patterning compositions is described, for example, inU.S. Pat. No. 9,310,684 to Meyers et al., entitled “OrganometallicSolution Based High Resolution Patterning Compositions,” incorporatedherein by reference. Refinements of these organometallic compositionsfor patterning are described in published U.S. patent applications2016/0116839 A1 to Meyers et al., entitled “Organometallic SolutionBased High Resolution Patterning Compositions and CorrespondingMethods,” and 2017/0102612 A1 to Meyers et al. (hereinafter the '612application), entitled “Organotin Oxide Hydroxide PatterningCompositions, Precursors, and Patterning,” both of which areincorporated herein by reference.

The radiation patterning performed with alkyl tin compositions generallyis performed with alkyltin oxo-hydroxo moieties. The compositionssynthesized herein can be effective precursors for forming the alkyl tinoxo-hydroxo compositions that are effective for high resolutionpatterning. The alkyltin precursor compositions comprise a group thatcan be hydrolyzed with water or other suitable reagent under appropriateconditions to form the alkyl tin oxo-hydroxo patterning compositions,which can be represented by the formula RSnO_((1.5-(x/2)))(OH)_(x) where0<x≤3. The hydrolysis and condensation reactions that can transform thecompositions with hydrolyzable groups (X) are indicated in the followingreactions:RSnX₃+3H₂O→RSn(OH)₃+3HX,RSn(OH)₃→RSnO_((1.5-(x/2)))OH_(x)+(x/2) H₂O.If the hydrolysis products HX are sufficiently volatile, in situhydrolysis can be performed with water vapor during the substratecoating process, but the hydrolysis reactions can also be performed insolution to form the alkyl tin oxo-hydroxo compositions. Theseprocessing options are described further in the '612 application.

Polyalkyl tin impurity compositions may affect condensation andcontribute to photoresist outgas sing during lithographic processing,which increases the potential for tin contamination of equipment usedfor film deposition and patterning. Based on these concerns, asignificant desire exists to reduce or eliminate the dialkyl or otherpolyalkyl components. Three classes of compositions are relevant for theprocessing described herein for the reduction of polyalkyl tincontaminants in ultimate resist compositions, specifically, monoalkyltin triamide, monoalkyl tin trialkoxide, and monoalkyl triamido tin. Asexplained further in the following, the monoalkyl tin triamidecompositions can also serve as precursors for the monoalkyl tintrialkoxide and monoalkyl triamido tin compositions. The monoalkyltriamido tin compositions can also be convenient precursors for formingthe monoalkyl tin trialkoxide compositions. The monoalkyl tintrialkoxide compositions can be desirable constituents in precursorpatterning composition solutions since they are amendable to in situhydrolysis and condensation to form monoalkyl tin oxo-hydroxocompositions with alcohol byproducts that are generally appropriatelyvolatile for removal commensurate with in situ hydrolysis.

The monoalkyl tin triamide compositions can be directly synthesized withrelatively low polyalkyl contaminants using any one of three methodsdescribed herein. The methods with Zn reagents were specificallydeveloped for synthesis of pure monoalkyl tin triamides containingsecondary alkyl groups. Furthermore, at least some of the monoalkyl tintriamide compositions can be further purified using fractionaldistillation. The synthesis of monoalkyl triamido tin compositions fromthe monoalkyl tin triamide compositions provides a further approach toreduce the polyalkyl contaminants. These approaches can be combined toresult in further reduction of polyalkyl contaminants.

The monoalkyl tin triamide compositions generally can be represented bythe formula RSn(NR′)₃, where R and R′ are independently an alkyl or acycloalkyl with 1-31 carbon atoms with one or more carbon atomsoptionally substituted with one of more heteroatom functional groupscontaining O, N, Si, and/or halogen atoms or an alkyl or a cycloalkylfurther functionalized with a phenyl or cyano group. In someembodiments, R′ can comprise ≤10 carbon atoms and can be, for example,methyl, ethyl, propyl, isopropyl, butyl, t-butyl, isobutyl, or t-amyl.The R group can be a linear, branched, (i.e., secondary or tertiary atthe metal-bonded carbon atom), or cyclic hydrocarbyl group. Each R groupindividually and generally has from 1 to 31 carbon atoms with 3 to 31carbon atoms for the group with a secondary-bonded carbon atom and 4 to31 carbon atoms for the group with a tertiary-bonded carbon atom. Inparticular, branched alkyl ligands can be desirable for some patterningcompositions where the compound can be represented as R¹R²R³CSn(NR′)₃,where R¹ and R² are independently an alkyl group with 1-10 carbon atoms,and R³ is hydrogen or an alkyl group with 1-10 carbon atoms. As notedbelow, this representation of alkyl ligand R is similarly applicable tothe other embodiments generally with R¹R²R³CSn(X)₃, with X correspondingto the trialkoxide or triamide moieties. In some embodiments R¹ and R²can form a cyclic alkyl moiety, and R³ may also join the other groups ina cyclic moiety. Suitable branched alkyl ligands can be, for example,isopropyl (R¹ and R² are methyl and R³ is hydrogen), tert-butyl (R¹, R²and R³ are methyl), tert-amyl (R¹ and R² are methyl and R³ is —CH₂CH₃),sec-butyl (R¹ is methyl, R² is —CH₂CH₃, and R³ is hydrogen), neopentyl(R¹ and R² are hydrogen, and R³ is —C(CH₃)₃), cyclohexyl, cyclopentyl,cyclobutyl, and cyclopropyl. Examples of suitable cyclic groups include,for example, 1-adamantyl (—C(CH₂)₃(CH)₃(CH₂)₃ or tricyclo(3.3.1.13,7)decane bonded to the metal at a tertiary carbon) and 2-adamantyl(—CH(CH)₂(CH₂)₄(CH)₂(CH₂) or tricyclo(3.3.1.13,7) decane bonded to themetal at a secondary carbon). In other embodiments hydrocarbyl groupsmay include aryl or alkenyl groups, for example, benzyl or allyl, oralkynyl groups. In other embodiments the hydrocarbyl ligand R mayinclude any group consisting solely of C and H and containing 1-31carbon atoms. For example: linear or branched alkyl (i-Pr ((CH₃)₂CH—),t-Bu ((CH₃)₃C—), Me (CH₃—), n-Bu (CH₃CH₂CH₂CH₂—)), cyclo-alkyl(cyclo-propyl, cyclo-butyl, cyclo-pentyl), olefinic (alkenyl, aryl,allylic), or alkynyl groups, or combinations thereof. In furtherembodiments suitable R groups may include hydrocarbyl groups substitutedwith hetero-atom functional groups including cyano, thio, silyl, ether,keto, ester, or halogenated groups or combinations thereof.

The alkyl tin trialkoxide compositions can be represented by the formulaRSn(OR⁰)₃, and the alkyl triamido tin compositions can be represented bythe formula RSn(NR″COR″′)₃. The R groups in the formulas for the alkyltin trialkoxide and alkyl triamido tin compositions can be the same Rgroups as summarized above for the alkyl tin triamide compositions, andthe corresponding discussion of these R groups above is as if copied inthis paragraph in its entirety. For the alkylamido (—NR″COR″′) oralkoxide ligands —OR⁰, the R″, R″′ and R⁰ groups can be independentlyhydrocarbon groups with 1-10 carbon atoms, such as methyl groups, ethylgroups, or the like. R″ and R″′ can independently also be hydrogen.

In some embodiments, the compositions (monoalkyl tin triamides,monoalkyl tin trialkoxides or monoalkyl triamido tin) herein can havedialkyl tin contaminants in amounts of no more than about 4 mole percentwith respect to tin, in further embodiments no more than about 3 molepercent, in some embodiments no more than about 2 mole percent, inadditional embodiments no more than about 1 mole percent dialkyl tincontaminants, in other embodiments no more than about 0.5 mole percentdialkyl tin contaminants, and in another embodiment no more than about0.1 mole percent. A person of ordinary skill in the art will recognizethat additional ranges of dialkyl tin contaminants within the explicitranges above are contemplated and are within the present disclosure. Thelevel of dialkyl tin contaminants can generally be performed using anyreasonable analytical technique. In some embodiments, the amount ofdialkyl tin diamide or dialkyl tin dialkoxide can be shown to be near orbelow 0.1 mole percent by quantitative NMR. As a result of potentialunidentified contaminants, the quantification of the monoalkyl tincompositions may be measured within a few percent, but the level oferror in the relatively small quantities for the dialkyl tincontaminants provides reliability using the quantitative NMR as noted inthe examples below.

The monoalkyl Sn precursors were analyzed without derivatization by ¹Hand ¹¹⁹Sn NMR spectroscopy. Integration values from NMR spectral peaksof a monoalkyl Sn precursor relative to an internal standard were usedto determine purity. Precautions were taken to ensure that the valuesaccurately reflected the purity of the monoalkyl Sn precursor.Calibrated 90-degree pulses were used to irradiate samples for ¹H NMRand inverse-gated ¹¹⁹Sn{¹H} NMR experiments. Additionally, for both ¹Hand ¹¹⁹Sn{¹H} NMR experiments, the T₁ relaxation values of the standardand analyte were measured with an inversion recovery experiment. Themeasured T₁ values were used to set recycle delay times equal to 5 timesthe longest T₁ time of the sample, which allows for nearly completerelaxation of the nuclei (Z=1−e^(−(elapsed time/T1))) to equilibrium(Z=1−e⁻⁵=0.99326). Finally, for ¹¹⁹Sn{¹H} NMR experiments, to accountfor the diminished intensity of spectral peaks that are not located atthe center of a spectral window, the B1 profile of the NMR spectrometerwas measured and accounted for by centering the spectrum between theanalyte and standard. Detection and quantification of trace Snimpurities were accomplished with a parameter set for inverse-gated¹¹⁹Sn{¹H} NMR spectroscopy that enhances the signal-to-noise ratio inthe spectra: the center and sweep width of the spectra were set to acalibrated value, and a 30-degree pulse was used to irradiate the samplewith the recycle delay time set to 1 second. Linear regression analysiswas used to assign quantitative values to the low-level Sn impuritiesthat were detected. The method provides a quantitation limit of 0.1% fordialkyl, tetrakis amide, and tetrakis alkoxide tin impurities relativeto monoalkyl tin compounds. Quantitative NMR is described further inWeber et al., “Method development in quantitative NMR towardsmetrologically traceable organic certified reference materials used as³¹P qNMR standards,” Anal. Bioanal. Chem., 407:3115-3123 (2015); andPauli et al., “Importance of Purity Evaluation and the Potential ofQuantitative ¹H NMR as a Purity Assay,” J. Medicinal Chemistry, 57,9220-9231 (2014), both of which are incorporated herein by reference.

In general, the improved processes herein for preparing monoalkyl tintriamides comprise reacting a compound having an alkyl donating group,also described as an alkylating agent, with a tin tetraamide. Desirableresults have been achieved in which the alkylating agent may be aGrignard reagent, a diorganozinc reagent, or a mono-organozinc amide.These syntheses can directly produce the monoalkyl tin triamides withlow polyalkyl contaminants that can be used for forming resists or thatcan be further purified to reduce the contaminant levels even further.In the synthesis methods, the alkylating agent selectively replaces anamide group of tin tetraamide with the alkyl group. In some embodiments,the reaction selectively produces monoalkyl tin triamide with lowpolyalkyl tin contaminants, particularly low dialkyl tin contaminants.The synthesis methods described improve the selectivity and yield ofmonoalkyl tin triamides by limiting the formation of dialkyl tinbyproducts. The methods are especially useful for branched alkylsystems. The monoalkyl tin triamides with low polyalkyl contaminants canthen be used to form monoalkyl tin trialkoxides with low polyalkylcontaminants. As discussed further below, the formation of crystallinemonoalkyl triamido tin compositions provides an alternative approach toavoid polyalkyl contaminants by their exclusion from the crystal.

For the reactions to form the monoalkyl tin triamide compounds, the tintetraamide compounds can be obtained commercially or synthesized usingknown techniques. For example, tetrakis(dimethylamido)tin, Sn(NMe₂)₄, isavailable form Sigma-Aldrich. For the synthesis of the monoalkyl tincompositions, the tin tetraamide reactant in solution generally can havea concentration of between about 0.025 M and about 5 M, in furtherembodiments between about 0.05 M and about 4 M, or in additionalembodiments between about 0.1 M and 2 M. A person of ordinary skill inthe art will recognize that additional ranges of reactant concentrationswithin the explicit ranges above are contemplated and are within thepresent disclosure. In general, the relevant reactions to introduce analkyl ligand to Sn can be initiated with the tin tetraamides in solutionin a reactor under inert gas purge and in the dark. In alternativeembodiments, some or all of the tin tetraamide reactant is addedgradually, in which case the concentrations above may not be directlyrelevant since higher concentrations in the gradually added solution maybe appropriate and the concentrations in the reactor may be transient.

The alkylating agent generally is added in an amount relatively close toa stoichiometric amount. In other words, the alkylating agent is addedto provide the molar equivalent of one alkyl group for one tin atom. Ifan alkylating agent can provide multiple alkyl groups, such as thediorganozinc compounds that can donate two alkyl groups per zinc atom,then the stoichiometric amount of the alkylating agent is adjustedaccordingly to provide about one alkyl group for each Sn. So, fordiorganozinc compounds on the order of one mole of Zn is required pertwo moles of Sn. The amount of the alkylating agent can be about ±25%,about ±20%, or about ±15% relative to the stoichiometric amount of thereagent, or in other words the stoichiometric amount of the reagent + or− a selected amount to achieve desired process performance. A person ofordinary skill in the art will recognize that additional ranges ofrelative amount of alkylating agent within the explicit ranges above arecontemplated and are within the present disclosure.

Examples 2 and 3 use approximately the stoichiometric amounts ofalkylating agent, while Example 1 and Example 4 use about 110% (or100%+10%) alkylating agent. The alkylating agent dissolved in organicsolvent can be added gradually to the reactor, such as dropwise orflowed at a suitable rate to control the reaction. The rate of additioncan be adjusted to control the reaction process, such as over the courseof time between about 1 minute to about 2 hours and in furtherembodiments from about 10 minutes to about 90 minutes. The concentrationof alkylating agent in the addition solution can be adjusted withinreasonable values in view of the rate of addition. In principle, thealkylating reagent can start in the reactor with the gradual addition ofthe tin tetraamide. A person of ordinary skill in the art will recognizethat additional ranges of alkylating agents and addition times withinthe explicit ranges above are contemplated and are within the scope ofthe present disclosure.

The reaction to introduce the alkyl ligand to the tin atom may beconducted in a low oxygen, substantially oxygen free, or an oxygen-freeenvironment, and an active inert gas purge can provide the appropriateatmosphere, such as an anhydrous nitrogen purge or an argon purge. Thefollowing additives have been observed to reduce addition of a secondalkyl group to tin: pyridine, 2,6-lutidine, 2,4-lutidine,4-dimethylaminopyridine, 2-dimethylamino pyridine, triphenylphosphine,tributylphosphine, trimethylphosphine, 1,2-dimethoxyethane, 1,4-dioxane,and 1,3-dioxane. Other neutral coordinating bases may function in thesame way. The reaction can optionally further comprise from about 0.25to about 4 moles of neutral coordinating base per mole of tin. Thereaction can be shielded from light during the reaction. The reactionmay be conducted in an organic solvent, for example, an alkane (such aspentane or hexane), an aromatic hydrocarbon (such as toluene), ether(such as diethyl ether, C₂H₅OC₂H₅), or mixtures thereof. The solvent maybe anhydrous to avoid reaction with water. The reaction generally is runfor about 15 minutes to about 24 hours, in further embodiments fromabout 30 minutes to about 18 hours and in additional embodiments fromabout 45 minutes to about 15 hours. The temperature during the reactionmay be between about −100° C. and about 100° C., in further embodimentsbetween about −75° C. and about 75° C., and in additional embodimentsbetween about −60° C. and about 60° C. Cooling or heating can be used tocontrol the reaction temperature within the desired range, and controlof the rate of reactant addition can also be used to influencetemperature evolution during the course of reaction. The productmonoalkyl tin triamide generally is an oil that can be purified usingvacuum distillation. Typical yields have been observed to beapproximately 50 to 85 percent. A person of ordinary skill in the artwill recognize that additional ranges of concentrations and processconditions within the explicit ranges above are contemplated and arewithin the present disclosure.

The alkylating agent may be a Grignard reagent, a diorganozinc reagent,or a mono-organozinc amide. A Grignard reagent can be anorgano-magnesium halide. Specifically, a Grignard reagent in thedescribed reaction may be RMgX, where X is a halide, generally Cl, Br,or I. R may be an alkyl or cycloalkyl and have between 1 and 31 carbonatoms, and generally R can be described more fully as above with respectto the R moiety of the product compositions, which is as if incorporatedfor this discussion in its entirety. For example, the alkyl orcycloalkyl may be branched, can comprise aromatic groups and/or may haveone or more heteroatom functional groups containing atoms such as O, N,Si, and/or a halogen. Grignard reagents are available commercially orcan be synthesized using known methods. Commercial sources includeAmerican Elements Company, Sigma-Aldrich, and many other suppliers.

In some embodiments, the alkylating agent is a diorganozinc reagent. Thediorganozinc reagent can donate two alkyl groups to tin, so the amountof diorganozinc reagent is adjusted for the difference in molarequivalents. Specifically, the diorganozinc reagent may be R₂Zn. R maybe an alkyl or cycloalkyl with between 1 and 31 carbon atoms. The Rgroup can be specified more fully as above with respect to the R moietyof the product compositions, and the discussion above for the R groupassociated with the product monoalkyl tin compounds is considered partof the present discussion as if reproduced here. For example, the alkylor cycloalkyl may be branched and may have one or more heteroatomfunctional groups containing atoms such as O, N, Si, and/or a halogen.Dicycloheptyl zinc ((C₇H₁₃)₂Zn) reactant is exemplified below.Diorganozinc compounds are available commercially or can be synthesizedusing known techniques. Commercial sources include, for example, AlfaAesar, Sigma-Aldrich, Rieke Metals (Nebraska, USA) and Triveni Chemicals(India). The reactant in the examples was synthesized.

In further embodiments the alkylating agent is a mono-organozinc amide(RZnNR′₂). R may be an alkyl or cycloalkyl generally having between 1and 30 carbon atoms. The R group can be specified more fully as abovewith respect to the R moiety of the product compositions, and thediscussion above for the R group associated with the product monoalkyltin compounds is considered part of the present discussion as ifreproduced here. For example, the alkyl or cycloalkyl may be branchedand may have one or more carbon atoms substituted with one or moreheteroatom functional groups containing atoms such as O, N, Si, and/or ahalogen. In some embodiments, R′ is an alkyl or cycloalkyl group, whichcan be substituted with a hetero-atom. In some embodiments, R′ may havebetween 1 and 8 carbon atoms, in some embodiments between 1 and 5 carbonatoms, and in additional embodiments between 1 and 3 carbon atoms. R′may be methyl, ethyl, propyl, isopropyl, butyl, iso-butyl, t-butyl, ort-amyl groups. The mono-organozinc amides can be synthesized, forexample, from an alkyl zinc halide (RZnX, X=I, Br, Cl) and lithium amide(LiNR′₂), which are commercially available reagents from Sigma-Aldrich.

The monoalkyl tin triamides produced using the methods described aboveor other methods not explicitly described herein can be further purifiedusing fractional distillation. To reduce the temperature of thedistillation process, the pressure can be reduced, for example, to apressure from about 0.01 Torr to about 10 Torr, in further embodimentsfrom about 0.05 Torr to about 5 Torr, and in further embodiments fromabout 0.1 Torr to about 2 Torr. A suitable fractional distillationcolumn can be used with a volume suitable for the process, and these arecommercially available. The temperature can be controlled in the vesselholding the material to be purified and along the column to achieve thedesired separation. The thermal conditions for one embodiment ispresented in Example 8 below, and these conditions can be readilygeneralized for other compositions based on the teachings herein. If thedialkyl tin triamide contaminants have a higher boiling point than themonoalkyl tin triamides, the monoalkyl tin triamides can be separatedaway during the distillation process. Fractions can be taken withvolumes of liquid removed during stages of the fractional distillation,but Example 8 demonstrates good separation with reasonable yield freefrom detectable contaminants. If the dialkyl tin triamide contaminantshave a lower boiling point than the monoalkyl tin triamides, the dialkyltin triamides can be separated away by collecting and discarding aninitial fraction during the distillation process.

Monoalkyl tin trialkoxides can be produced by reacting the correspondingmonoalkyl tin triamide with an alcohol in a non-aqueous solvent and abase. The low polyalkyl tin contaminants in the monoalkyl tin triamidesusing the processing described herein can be carried forward into theproduct monoalkyl tin trialkoxides, so that the product monoalkyl tintrialkoxides have low dialkyl tin contaminants essentially at the molepercentages described above. Suitable organic solvents include, forexample, an alkane (such as pentane or hexane), an aromatic hydrocarbon(such as toluene), ether (such as diethyl ether, C₂H₅OC₂H₅), or mixturesthereof. The alcohol is selected to provide the desired alkoxide groupsuch that an alcohol ROH introduces the —OR group as the ligand attachedto tin. A list of suitable R groups is provided above andcorrespondingly relate to the alcohol. Examples are provided below witht-amyl alcohol, but other alcohols can be similarly used to provide thedesired —OR alkoxide ligand. The alcohol can be provided roughly in astoichiometric amount. Since the alcohol is used to replace three amidegroups, three mole equivalents of alcohol would be a stoichiometricamount. In general, the amount of alcohol can be at least about −5%stoichiometric equivalents and in further embodiments at least about astoichiometric equivalent, and a large excess of alcohol can be used.Example 5 is performed with +3.33% over the stoichiometric equivalent ofalcohol, i.e., 3.1 moles alcohol per mole of mono-alkyl tin triamide. Tofacilitate purification of the product alkyl tin trialkoxide, atetradentate chelating agent can be added to coordinate with unreactedspecies to form complexes that do not vaporize during distillation. Forexample, tri(2-aminoethyl)amine (TREN), triethylenetetraamine (trien),or other tertadentate non-planar coordination ligands can be used tocomplex with the unreacted species to facilitate purification. Thecoordination ligand can be added at a selected time from the start ofthe reaction to any time prior to performing the distillation, in anamount from about 0.5 mole % to about 15 mole % and in furtherembodiments from about 1.0 mole % to about 10 mole % relative to the tinmolar quantity. A person of ordinary skill in the art will recognizethat additional ranges of reactant amounts within the explicit rangesabove are contemplated and are within the present disclosure. Ifdesired, a fractional distillation can be performed to further purifythe monoalkyl tin trialkoxides from polyalkyl contaminants.

While the monoalkyl tin triamide with low polyalkyl contaminants can beused effectively to form derivatives with correspondingly low polyalkylcontaminants, the synthesis of a mono-alkyl triamido tin from themonoalkyl tin triamide can be used to form a low contaminant producteven if the monoalkyl tin triamide does not have a low contaminantlevel, which is due to the formation of crystals of the monoalkyltriamido tin that evidently can exclude the polyalkyl contaminants.Thus, the synthesis of the monoalkyl triamido tin provides asupplemental or an alternative pathway to form compositions with lowdialkyl tin contaminants. Therefore, in some embodiments, monoalkyl tintriamides with higher than desired contaminants, such as from commercialsources or reaction pathways with higher contaminant levels, can be usedwhile still obtaining product compositions with low dialkyl tincontaminants. The monoalkyl triamido tin compounds can be used to formmonoalkyl tin trialkoxide compositions with low dialkyl tincontaminants.

The reaction involves the addition of N-alkylamide, such asN-methylacetamide (CH₃CONHCH₃), to the monoalkyl tin triamide. Ingeneral, the N-alkylamide reactant can be written as R^(a)CONHR^(b),where R^(a) and R^(b) are independently hydrocarbon groups with 1 to 10carbon atoms, such as methyl groups, ethyl groups, propyl groups,isopropyl groups, or the like. The crystal structure of the productcompound has been determined, and the structure is presented in theExamples below. In summary, the amide groups in the product are bound tothe tin at the nitrogen atom to form the corresponding ligand structure.

To control heat production and progress of reaction, the N-alkylamidereactant can be added gradually, such as over at least about 2 minutes.The monoalkyl tin triamide can be dissolved in an organic solvent at aconcentration from about 0.1M to about 8M and in further embodimentsfrom about 0.2M to about 6M. Suitable organic solvents include, forexample, an alkane (such as pentane or hexane), an aromatic hydrocarbon(such as toluene), ether (such as diethyl ether, C₂H₅OC₂H₅), or mixturesthereof. The reaction is exothermic, and heat generally does not need tobe added. The reaction product can form crystals, and the reaction canbe continued generally from about 20 minutes to 24 hours. Aftercompletion of the reaction, the solvent can be removed to collect thecrystals of the product. The crystals can be washed and dried. Thedialkyl tin compounds are observed to be excluded from the productcrystal. A person of ordinary skill in the art will recognize thatadditional ranges of reactant concentrations, addition times, andreaction times within the explicit ranges above are contemplated and arewithin the present disclosure.

For the processing of radiation sensitive resist compositions, it can bedesirable to react the monoalkyl triamido tin to form monoalkyl tintrialkoxide compounds. An alkali alkoxide can be used to replace thetriamido ligands with alkoxide ligands through reaction in an organicslurry. As the monoalkyl tin trialkoxide compound forms, it dissolves inthe organic solvent in a concentration from about 0.01M to 2M and infurther embodiments from about 0.04M to about 1M. The alkali alkoxidecompound can be written as ZOR′, where Z is an alkali atom, such as K,Na, or Li, and —OR′ is the alkoxide group that provides thecorresponding R′ group for the RSn(OR′)₃ product composition. Somealkali alkoxides are available commercially, for example, fromSigma-Aldrich, and these compounds are highly hygroscopic, so they canbe isolated from air. Suitable organic solvents include, for example, analkane (such as pentane or hexane), an aromatic hydrocarbon (such astoluene), ether (such as diethyl ether, C₂H₅OC₂H₅), or mixtures thereof.The alkali alkoxide can be provided in at least a stoichiometric amount,which corresponds to three alkoxide groups per tin atom. The reactioncan be carried out for from about 15 minutes to about 48 hrs. Theproduct liquid can be distilled to purify the product. A person ofordinary skill in the art will realize that additional ranges ofconcentration and time within the explicit ranges above are contemplatedand are within the scope of the present disclosure.

EXAMPLES Example 1: Synthesis of t-BuSn(NMe₂)₃

This example is directed to the synthesis of the tin compound with at-butyl group bonded to the tin replacing an N-methyl amide group.

A 5 L 3-neck round bottom flask was charged with Sn(NMe₂)4 (827.5 g,2805 mmol, Sigma) in an argon-filled glovebox. Anhydrous ether (2000 mL)was added to the flask. A quantity of t-BuMgCl (1500 mL, 2.06 M (freshlytitrated), 3090 mmol) was added to a separate 2 L 2-neck round bottomflask. The flasks were stopped and attached to a Schlenk line. TheSn(NMe₂)₄ solution was transferred to a 5 L jacketed reactor and stirredat 240 RPM. An automated syringe pump was used to deliver the t-BuMgClsolution to the 5 L jacketed reactor at a rate of 50 ml min⁻¹. Thetemperature of the mixture in the jacketed reactor was maintained at 20°C. After complete addition of the t-BuMgCl solution, the reaction wasstirred overnight. The resulting mixture was transferred through at 10 Lfilter reactor into a 5 L 3-neck round bottom flask equipped with a stirbar. The 5 L jacketed reactor and the solids in the filter reactor wererinsed with pentane (2×1 L). The washings were collected in the 5 L3-neck round bottom flask equipped with a stir bar and the volatileswere removed under vacuum. After the volatiles were removed, a lightyellow oily suspension corresponding to the crude product was observed.The flask was taken into a glovebox and the crude product was filteredthrough a course porosity fritted funnel. The filtrate was transferredinto a 2 L 2-neck round bottom flask equipped with a stir bar, which wasstoppered and transferred to a Schlenk line. The crude product waspurified by short-path vacuum distillation into a 1 L receiving flask(500 mTorr, 65° C.-75° C.) to give 323-604 g, 37-70% of a colorless oilidentified as t-BuSn(NMe₂)₃. Proton NMR (FIG. 1) and ¹¹⁹Sn NMR (FIG. 2)were performed to characterize the product with the following peaksobserved: ¹H NMR (C₆D₆, MHz): 2.84 (s, 18H, —NCH₃), 1.24 (s, 9H, H₃CC—);¹¹⁹Sn NMR (C₆D₆, 186.4 MHz: −85.69. Quantitative proton NMR and tin NMRwere performed to evaluate the purity of the product based on astandard. qNMR: ¹H, standard 1,3,5-trimethoxybenzene, purity 94.5(3)mole % (94.5±0.3 mole %) monoalkyl tin; ¹¹⁹Sn, standard MeSnPh₃, purity93.5(2) mole % monoalkyl tin.

¹¹⁹Sn qNMR on trace impurities:

% impurity/tBuSn(NMe₂)₃ Impurity I_(impurity)/I_(t-BuSn(NMe2)3) (molmol⁻¹) tBu₂Sn(NMe₂)₂ 2.2 × 10⁻² 2.6(1)  Sn(NMe₂)₄  3 × 10⁻³ 0.1(1)**value calculated from extrapolation from calibration curve.

Example 2: Synthesis of CySn(NMe₂)₃ (Cy=cyclohexyl)

This example is directed to the synthesis of the tin compound with acyclohexyl group from a Zn reagent replacing an N-methyl amide group ofSn(NMe₂)₄.

A 250 mL 3-neck round bottom flask (RBF) was charged with Sn(NMe₂)₄(5.61 g, 19.0 mmol, Sigma) in an argon-filled glovebox. Anhydrous ether(150 mL) was added to the flask. Separately, a 100 mL RBF was chargedw/LiNMe₂ (0.97 g, 19.0 mmol, Sigma) and anhydrous ether (20 mL). CyZnBr(Cy=cyclohexyl, 48.5 mL, 0.392M, 19.0 mmol, Sigma]) was added slowly tothis flask to produce CyZnNMe₂. The CyZnBr was added slowly to controlthe reaction temperature because the reaction is exothermic. A droppingfunnel and reflux condenser were attached under an active argon purge tothe 3-neck 250 mL RBF on the Schlenk line. The CyZnNMe₂ solution wasadded to the dropping funnel and dispensed dropwise with stirring whilethe 250 mL RBF was covered with aluminum foil to keep out light. Aftercomplete addition, the reaction was stirred overnight and the solventremoved in vacuo to give a pale orange oil with a precipitate. The oilwas purified by vacuum distillation (58-62° C., 150 mtorr). Theresulting product was 4.38 g (69% yield) of a colorless oil identifiedas CySn(NMe₂)₃. Proton NMR (FIG. 3) and ¹¹⁹Sn NMR (FIG. 4) characterizethe product with the following peaks observed: ¹H NMR (C₆D₆, 500 MHz):2.85 (s, 18H, —NCH₃), 1.86 (m, 3H, —CyH), 1.69 (m, 2H, —CyH), 1.53 (m,3H, —CyH), 1.24 (m, 3H, —CyH); ¹¹⁹Sn NMR (C₆D₆, 186.4 MHz): −73.77.

Example 3. Synthesis of (CyHp)Sn(NMe₂)₃ (CyHp=cycloheptyl)

This example is directed to the synthesis of a tin triamide with acycloheptyl group, as shown in the following formula. In this synthesis,a cycloheptyl group from the zinc reagent (CyHp)₂Zn replaces an N-methylamide group of Sn(NMe₂)₄.

A 250 mL 3-neck round bottom flask (RBF) was charged with Sn(NMe₂)₄(6.49 g, 22.0 mmol, Sigma) in an argon-filled glovebox. Anhydrous ether(150 mL) was added. A dropping funnel and reflux condenser were attachedunder an active argon purge to the 3-neck 250 mL RBF on a Schlenk line.Separately prepared (CyHp)₂Zn (0.351M, 31.3 mL, 11.0 mmol) wassynthesized as follows: 2 CyHpMgBr+Zn(OCH₃)₂. The (CyHp)2Zn solution wasadded to the dropping funnel under active argon purge and then dispenseddropwise with stirring while the 250-mL RBF was covered with aluminumfoil to keep out light. After complete addition, the reaction wasstirred overnight. The solvent was then removed in vacuo. The reactionflask was taken into a glovebox and hexane was added. The solution wasfiltered over Celite® and the solvent removed in vacuo to give acolorless oil with precipitate. The oil was purified by vacuumdistillation (82-86° C., 180 mtorr). The resulting product was 4.01 g(52% yield) of a colorless oil identified as (CyHp)Sn(NMe₂)₃. Proton NMR(FIG. 5) and ¹¹⁹Sn NMR (FIG. 6) were performed to characterize theproduct with the following peaks observed: ¹H NMR (C₆D₆, 500 MHz): 2.84(s, 18H, —NCH₃), 2.01 (m, 2H, —CyHpH), 1.82 (m, 1H, —CyHpH), 1.69-1.23(m, 10H, —CyHpH); ¹¹⁹Sn NMR (C₆D₆, 186.4 MHz): −66.93.

Example 4. Preparation of t-BuSn(NMe₂)₃ with Added Base

This example demonstrates the synthesis of the tin composition viareaction of a Grignard reagent with Sn(NMe₂)₄ in the presence of a base.

A 5-L, 3-neck RBF was charged with Sn(NMe₂)₄ (539.0 g, 1.827 mols,Sigma) in an argon-filled glovebox. Approximately 3 L of anhydrousdiethyl ether and pyridine (289.1 g, 3.66 mols) were added to the flask.The flask was stoppered with glass stoppers on two of the necks and avacuum adapter was attached to the third. Separately, a 2-L, 2-neck RBFwas charged with 1 L of t-BuMgCl (Grignard reagent) as measured with avolumetric flask (2.01M (titrated), 2.01 mols, Sigma). On anargon-filled Schlenk line, a 5-L jacketed Chemglass™ reactor was preppedfor a high vacuum and heat reaction. The reactor was backfilled withargon, and the jacket around the reactor vessel was then cooled to −30°C.

The contents of the 5-L, 3-neck RBF were transferred to the Chemglass™reactor through polyethylene (PE) tubing under positive argon pressure.Stirring was commenced with an overhead stirrer, and the temperature ofthe reaction was allowed to cool to −15° C. On the Schlenk line, theGrignard reagent was added through polyethylene (PE) tubing withpositive argon pressure over the course of 20-30 minutes, while theinternal reaction temperature was maintained below 5° C. A dark orangecolor and precipitate developed. After complete addition, the reactionwas stirred overnight and allowed to come to room temperature whilekeeping the reaction shielded from light with aluminum foil.

After overnight reaction, the reaction color was light yellow. Thesolvent was removed in vacuo with the aid of a heating jacket at 30-35°C. After removal of the solvent, anhydrous pentane (˜2.5 L) was added tothe reactor via polyethylene tubing under positive argon pressure andthe solids mixed thoroughly with the overhead stirrer. The reactionproducts dispersed in the pentane were transferred via polyethylenetubing to a 10-L filter reactor with positive argon pressure. Thereaction products were filtered and then transferred throughpolyethylene tubing into a 3-L RBF. The pentane solvent was removed invacuo from the resultant light-yellow filtrate to leave a yellow oil.The oil was transferred to a 1-L Schlenk flask and vacuum distilled witha shortpath distillation head (50-52° C., 300 mtorr), yielding 349.9 g(62%) of a colorless oil. FIGS. 7 (¹H NMR) and 8 (¹¹⁹Sn NMR) areanalogous to FIGS. 1 and 2 and show the product consists of monoalkylspecies in equilibrium with Sn(NMe₂)₄. Quantitative proton NMR and tinNMR were performed with a selected standard to evaluate the purity ofthe product. qNMR: ¹H, standard 1,3,5-trimethoxybenzene, purity 89.9(7)mole % monoalkyl tin; ¹¹⁹Sn, standard MeSnPh₃, purity 93.6(4) mole %monoalkyl tin.

¹¹⁹Sn qNMR on trace impurities:

% impurity/tBuSn(NMe₂)₃ Impurity I_(impurity)/I_(t-BuSn(NMe2)3) (molmol⁻¹) tBu₂Sn(NMe₂)₂  2 × 10⁻³ 0.1(1)* Sn(NMe₂)₄ 2.4 × 10⁻² 2.3(1) *value calculated from extrapolation of calibration curve

Example 5. Preparation of High-Purity Monoalkyl Alkoxide t-BuSn(OtAm)₃from t-BuSn(NMe₂)₃

This example demonstrates the synthesis of monoalkyl tin trialkoxidefrom the corresponding monoalkyl tin triamide according to the followingreaction.

In a glovebox, a 2-L, 2-neck RBF was charged with ˜500-mL pentane andt-BuSn(NMe₂)₃ (329.4 g, 1.07 mol) from Example 4. The flask was tared ona balance, and tris(2-aminoethyl)amine (3.91 g, 26.7 mmol) was added viasyringe directly into the reaction mixture. The amine complexes andremoves tin tetrakisamide during reaction and purification. If it is notnecessary to remove tin tetrakisamide from the system, the product ofExample 1 may be used to synthesize additional monoalkyl tin products.The reaction sequence may be continued with the material synthesizedaccording to Example 1. A magnetic stir bar was added, and the reactionwas then sealed and brought to a Schlenk line. The flask was cooled in adry ice/isopropanol bath. Separately, a 1-L Schlenk flask was chargedwith 2-methyl-2-butanol (292.2 g, 3.315 mols) and a small amount ofpentane and then attached to the Schlenk line. The alcohol/pentanesolution in the Schlenk flask was transferred via cannula to thereaction flask with an outlet purge to a mineral oil bubbler connectedin line to an acid trap solution for the off-gassed NMe₂H. Aftercomplete addition of the alcohol, the reaction was allowed to come toroom temperature and stirred for 1 hour. After 1 hour of reaction, thesolvent was removed in vacuo, and the product was vacuum distilled(95-97° C., 500 mtorr) to yield 435 g (93%) of a colorless oil. FIGS. 9(¹H NMR) and 10 (¹¹⁹Sn NMR) show NMR spectra for the final productt-BuSn(Ot-Am)₃ with the following peaks observed: ¹H NMR (C₆D₆, 500MHz): 1.61 (m, 6H, —OC(CH₃)₂CH₂), 1.37 (m, 18H, —OC(CH₃)₂), 1.28 (s, 9H,—C(CH₃)₃), 1.01 (m, 9H, —OC(CH₃)₂CH₂CH³); ¹¹⁹Sn NMR (C₆D₆, 186.4 MHz):−240.70. Quantitative proton NMR was performed to evaluate the puritylevel of the product. qNMR: ¹H, standard 1,3,5-trimethoxybenzene, purity97.7(3)%; ¹¹⁹Sn, standard MeSnPh₃, 99(1) mole % monoalkyl tin.

Example 6. Preparation of t-butyltris(N-methylacetamido)tin(IV)

This example demonstrates the synthesis of monoalkyl triamido tincompositions by the reaction of t-BuSn(NMe₂)₃ with N-methylacetamide.

In a glovebox, a 250-mL Schlenk round bottom flask was charged witht-BuSn(NMe₂)₃ containing 1% t-Bu₂Sn(NMe₂)₂ (40.13g, 130 mmol).t-BuSn(NMe₂)₃ was synthesized by Example 1 or Example 4. Fiftymilliliters of toluene were added to the round bottom flask, which wasfollowed by slow addition of N-methylacetamide (28.6 g, 391 mmol, Sigma)to control heat production. An additional 30 mL of toluene was used towash all the N-methylacetamide into the reaction flask. The flask wassealed with a ground glass stopper and transferred to the Schlenk line.Over a period of several hours, large crystals precipitated fromsolution. The toluene was removed via cannula under an active argonpurge. White crystals were harvested and rinsed twice with 100 mLpentane using cannula addition and subsequent removal. They were driedin vacuo yielding 40.6 g (80%) of t-butyltris(N-methylacetamido)tin(IV).FIG. 11 shows the crystal structure of the solid determined by X-raydiffraction. As shown in FIG. 12, the proton NMR spectrum produces thefollowing peaks: ¹H NMR (C₆D₆, 500 MHz): 2.52 (s, 9H, —NCH₃), 2.01 (m,2H, —CyHpH), 1.74 (s, 9H, —(H₃C)₃CSn), 1.69 (s, 9H, —CH₃CO). As shown inFIG. 13, a tin NMR spectrum results in the following peaks: ¹¹⁹Sn NMR(C₆D₆, 186.4 MHz): −346.5.

Example 7. Synthesis of t-BuSn(Ot-Am)₃

This example demonstrates the synthesis of t-BuSn(Ot-Am)₃ from thet-butyltris(N-methylacetamido)tin(IV) product of Example 6.

In a glovebox with argon atmosphere, a 3-L round bottom flask wascharged with t-butyltris(N-methylacetamido)tin(IV) (100 g, 255 mmol)from Example 6 followed by addition of NaOtAm (98 g, 890 mmol, Sigma).The mixture was slurried in 1.5 L of pentane using a magnetic stirrerand 2.5-inch long egg-shaped stir bar. The slurry thickened and turned amilky-white color after 30-60 minutes. Stirring was continued forapproximately 16 h. The slurry was then filtered through a mediumporosity fitted funnel in the glovebox, and the recovered solids werewashed twice with 100 mL of pentane. The retained solids formed a veryfine cake during filtration, so stirring was occasionally used tofacilitate collection.

The filtrate was transferred to a two-neck 2-L flask equipped with astir bar, and the flask was then sealed with a ground-glass stopper andSchlenk-inlet adapter. The flask was removed from the glovebox andconnected to a vacuum line in a fume hood where excess solvent wasstripped under vacuum. The crude product was then purified by vacuumdistillation and collected in a 100-mL Schlenk storage flask. For thevacuum distillation, the oil bath was set to 150° C. The product wasdistilled at 300 mTorr and a temperature of 98-102° C. to yield 74 g(66%) of product. As shown in FIG. 14, a proton NMR spectrum displayedthe following shifts: ¹H NMR shifts [400 MHz, C₆D₆]: 1.64 (q, 6H, —CH₂),1.39 (s, 18H, —C(CH₃)₂), 1.29 (s, 9H, (CH₃)₃CSn), 1.03 (t, 9H, —CCH₃).As shown in FIG. 15, the ¹¹⁹Sn NMR spectrum displayed the followingpeaks: ¹¹⁹Sn NMR shifts [149.18 MHz, C₆D₆]: −241.9. Quantitative NMR wasperformed to evaluate the purity following evaluation of a standard. ¹HqNMR, standard 1,3,5-trimethoxybenzene, purity 97.3(1) mole % monoalkyl.

¹¹⁹Sn qNMR on trace impurities:

% impurity/tBuSn(OtAm)₃ Impurity I_(impurity)/I_(t-BuSn(OtAm)3) (molmol⁻¹) tBu₂Sn(OtAm)₂ 2 × 10⁻³ 0.1(2) Sn(OtAm)₄ (not detected) 0.0(3)

Example 8. Fractional Distillation Purification

This example demonstrates the effectiveness of fractional distillationto purify t-BuSn(NMe₂)₃ by its separation from a mixture oft-Bu₂Sn(NMe₂)₂ and t-BuSn(NMe₂)₃.

In a glovebox, a 3000-mL 3-Neck round bottom flask (RBF) was chargedwith t-BuSn(NMe₂)₃ containing ˜3.27% t-Bu₂Sn(NMe₂)₂ (total 1420 g, 4.6mols); the sample was prepared by the method described in Example 1 witha modified t-BuMgCl:Sn(NMe₂)₄ ratio. Glass stoppers were placed in twonecks of the RBF, and the third was attached to a Schlenk line.Separately, a 5-L Chemglass jacketed reactor was fitted with an overheadstirrer, temperature probe, and two 18-inch distillation columns stackedone atop the other. The distillation columns were filled with Pro-Pak™(ThermoScientific, 0.24 in²) high efficiency distillation columnpacking. A shortpath distillation head with temperature probe wasattached to the top of the distillation columns. The top of theshortpath head was then connected to a 3-arm cow joint holding three500-mL Schlenk bombs. The reactor was evacuated and back filled withargon three times. The t-Bu₂-rich mixture was added to the reactor vialarge cannula under argon. The jacketed reactor was heated between 110and 120° C. at reduced pressure (500 mTorr) to initiate distillation.The temperature at the bottom of the distillation column was measured tobe 95-100° C., while the temperature at the top of the column wasmaintained between 58 and 60° C. Three fractions were collected, andeach was analyzed via ¹¹⁹Sn NMR spectroscopy. FIGS. 16-19 are plots ofthe ¹¹⁹Sn NMR spectra for the pooled sample (FIG. 16) and each of thethree fractions (FIGS. 17-19 in order). All three fractions showed noNMR signals for t-Bu₂Sn(NMe₂)₂. Total yield, combining all fractions was850 g (60%). ¹¹⁹Sn NMR (C₆D₆, 186.4 MHz): −85.45

The embodiments above are intended to be illustrative and not limiting.Additional embodiments are within the claims. In addition, although thepresent invention has been described with reference to particularembodiments, those skilled in the art will recognize that changes can bemade in form and detail without departing from the spirit and scope ofthe invention. Any incorporation by reference of documents above islimited such that no subject matter is incorporated that is contrary tothe explicit disclosure herein. To the extent that specific structures,compositions and/or processes are described herein with components,elements, ingredients or other partitions, it is to be understood thatthe disclosure herein covers the specific embodiments, embodimentscomprising the specific components, elements, ingredients, otherpartitions or combinations thereof as well as embodiments consistingessentially of such specific components, ingredients or other partitionsor combinations thereof that can include additional features that do notchange the fundamental nature of the subject matter, as suggested in thediscussion, unless otherwise specifically indicated.

What is claimed is:
 1. A method for forming monoalkyl triamido tin, themethod comprising, reacting a monoalkyltin triamide compound representedby the chemical formula RSn(NR′₂)₃ with an amide (R″CONHR″′) in anorganic solvent, wherein R is a hydrocarbyl group with 1-31 carbonatoms, and wherein R′, R″ and R″′ are independently a hydrocarbyl with1-8 carbon atoms; and collecting a solid product represented by theformula RSn(NR″′COR″)₃.
 2. The method of claim 1 wherein the monoalkyltin triamide is at an initial concentration from about 0.1M to about 8Mand wherein the solvent is an alkane, an aromatic hydrocarbon, or anether.
 3. The method of claim 1 wherein the amide is added graduallyover a period of at least about 2 minutes.
 4. The method of claim 1wherein the solid product is crystalline and has no more than about 1mole percent relative to tin of contaminants of dialkyltin compounds. 5.The method of claim 1 wherein the monoalkyl triamido tin compound isselectively formed with no more than 1 mole percent polyalkyl tincontamination.
 6. The method of claim 1 wherein the monoalkyltintriamide compound has a dialkyl tin contamination that is no more thanabout 4 mole percent.
 7. The method of claim 1 wherein the monoalkyltintriamide compound has a polyalkyl tin contamination that is no more than1 mole percent.
 8. The method of claim 1 wherein R is a t-butyl group ora cyclohexyl group or a cycloheptyl group and R′ is a methyl group. 9.The method of claim 1 wherein R is a t-amyl group or an iso-propylgroup.
 10. The method of claim 8 wherein R″ and R″′ are methyl groups.11. A method for forming a monoalkyl tin trialkoxide compound, themethod comprising, reacting a monoalkyl triamido tin compound(RSn(NR″′COR″)₃) with an alkali alkoxide compound (QOR′, where Q is analkali metal atom) in an organic solvent to form a product compoundrepresented by the chemical formula RSn(OR′)₃, wherein R is ahydrocarbyl group with 1-31 carbon atoms and wherein R′, R″ and R″′ areindependently a hydrocarbyl group with 1-10 carbons.
 12. The method ofclaim 11 wherein the alkali alkoxide compound is provided in at least astoichiometric amount.
 13. The method of claim 11 wherein the solvent isan alkane, an aromatic hydrocarbon, or an ether.
 14. The method of claim11 wherein the monoalkyl tin trialkoxide compound is selectively formedwith no more than 1 mole percent polyalkyl tin contamination.
 15. Themethod of claim 11 wherein the monoalkyl triamido tin compound has a nomore than 1 mole percent polyalkyl tin contamination.
 16. The method ofclaim 11 wherein R is a t-butyl group or a cyclohexyl group or acycloheptyl group.
 17. The method of claim 11 wherein R is a t-amylgroup or an iso-propyl group.
 18. The method of claim 11 wherein R′ is atert-amyl group.
 19. The method of claim 11 wherein R″ and R″′ aremethyl groups.
 20. The method of claim 11 wherein Q comprises K, Na, Li,or combinations thereof.